Shackle angle?

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roadrunnerh

roadrunnerh

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I hope this post makes sense......

When I spoke with Dr. Diff a few weeks back, I asked about rear suspension, specifically...
Should the shackles after installation run straight up and down, lean forward, or lean back?
He was adamant that the bottom of the shackle should be closer to the rear like this / on left side of car rather than facing forward like this \.

On my Scamp they are close to straight but lean forward like this \ looking at the left side of car.
However, on my Road Runner Left / and right \

Any opinions here? What do you guys think?
 
I forget which it is, but the mopar suspension book has all the correct answers there. Mancini's. Ten bucks.
 
Here's the thing. When a leaf is compressed to the maximum, as like when you hit a bump or overload the trunk, they become FLATTER and LONGER. This will force the shackles as far to the rear (at the bottom of the shackle) as they will get.

BUT when you jack up the car and let the rear axle hang, OR you are driving, go over a huge bump and unload the rear axle, IE so bad that the axle might even become airborne (Come ON we've ALL done it!!!)

At that point the springs have maximum arch and are the SHORTEST so the shackles are FORWARD at the bottom

Now in the case of poor design, spring mods, different springs, relocated shackle mounts, etc, etc, You can reach a point where the shackles go "over center" and snap back in such a way, ---front or rear--- that the bottom of the shackle is reversed and up against the frame.

It's important to realize that this can happen if the springs are excessively short OR long in relation to the mounts

And, according to the manual Stroker mentioned above:

With the car sitting at static (level) the rear shackle should have the bottom spring eye slightly to the rear of the top pivot, or acceptable if vertical, NEVER with the lower eye in front of the top pivot.
 
Thanks dude. I thought that was it, but I didn't have my manual in front of me to verufy so I didn't want to give out wrong info.
 
rearsusp1.jpg
 
So how am I supposed to adjust it to make it correct???

I have brand new XHD springs, new shackles, new front hangers, new bushings, new shocks and shock plates, new U bolts.
 
With your sign language in the first post, I am confused. Which way is it off? In plain ingles, please.
 
Move the frame mount forward or back. Of course I would make sure both springs are the correct one's.
 
67Dart273 said:
... OR you are driving, go over a huge bump and unload the rear axle, IE so bad that the axle might even become airborne (Come ON we've ALL done it!!!):burnout:
YEEEE-HAWWW!! (the sound of valves floating & a severely over-revved engine in the background)...
Click to expand...
 
Ok, here are some pics on the subject.....Stroker, I thought my sign language was clever, no? :D
First pic is left side, second right side, third new ride height, fourth is the 8.75 installed.
 

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That shackle angle with the car on the ground?

How old are the springs? Could settle some and put them vertical

Can always space that rear shackle mount some to get the right angle.
 
I think I would give the springs some time to settle. If you have to you can shim the bracket.

Personally, I would drive it like I stole it.

Nice looking job by the way!
 
I had some 3/4" steel blocks with corresponding mounting bolt holes made to fit between the spring mounts and where it bolts to the frame. Of course you'll need longer bolts to compensate for the thicker mounting pad. This moved the pivot forward and the bottom of the shackle was angled further back.

I suppose aluminum blocks would work but liked the extra weight and strength of steel back there.
 
Lonewolf3165 said:
67Dart273 said:
... OR you are driving, go over a huge bump and unload the rear axle, IE so bad that the axle might even become airborne (Come ON we've ALL done it!!!):burnout:
YEEEE-HAWWW!! (the sound of valves floating & a severely over-revved engine in the background)...
Click to expand...


Yeah you know you've been there. LOL
Click to expand...
 
Those springs will settle a bit especially the more you romp off the launch pad, mine were the same as yours at first.

You can remove the rear spring clamps which will let the springs expand and settle in quicker wich will plant the springs better for hard launches but you may compromise sis by side spring integrity upon cornering.

Did you torque you U bolts properly?
The manual says 45 lb/ft but I like to go a little snugger than that.

Too tight can cause thumping or hopping and possibly distort the axle tubes.

Too loose can cause all kinds of problems.
 
i think its fine. after i had my leaf springs re-arched on my charger, the shackles sit the same way.
 
Thanks guys! I can always count on the members of FABO.
You guys know your stuff!
The springs are brand new XHD from Mancini's.
I'm glad some of you said they would settle. I was hoping so.
 
Lonewolf3165 said:
67Dart273 said:
... OR you are driving, go over a huge bump and unload the rear axle, IE so bad that the axle might even become airborne (Come ON we've ALL done it!!!):burnout:
YEEEE-HAWWW!! (the sound of valves floating & a severely over-revved engine in the background)...
Click to expand...

'S even MORE fun back when the ol' 340 powered Landcruiser...........
Click to expand...
 
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